1. Field of the Disclosure
Embodiments of the present disclosure relate to second order intermodulation product (IIP2) calibration technologies.
2. Description of the Related Art
A mixer may include a down-conversion mixer for converting a high frequency signal per gigahertz (GHz) or megahertz (MHz) into a low frequency signal of a few kilohertz (kHz), and an up-conversion mixer for converting a low frequency signal into a high frequency signal. The down-conversion mixer may be directly associated with sensitivity.
If a local oscillator (LO) frequency and two or more radio frequency (RF) signals are input to the mixer, a signal of a 2nd intermodulation (IMD) term may be generated. The signal of the 2nd IMD term may greatly interfere with a signal that is analyzed as a receive component by a signal transceiver and may result in deterioration in sensitivity. A design of a mixer with an excellent 2nd IMD characteristic is of great importance in a wireless communication system.
An IIP2 may be used as an index for a mixer, indicating how large a 2nd IMD component is. Since an undesirable signal (e.g., a leakage signal) is of a higher level, a signal of a 2nd IMD term may be increased to a greater extent. If an IIP2 index is high, since the signal of the 2nd IMD term is reduced, there may be a gain in view of reception performance.
If there is an external leakage signal, ensuring performance of an IIP2 index may be very important in enhancing performance of receive sensitivity. To ensure IIP2 performance with respect to some time division duplex (TDD) bands, a method of calibrating an IIP2 in a board may be used. The method of calibrating the IIP2 in the board may be diverse according to a register structure or the like in terms of a mixer design scheme, a modem, or software.
If a degree of leakage is large with respect to a frequency division duplex (FDD) band, a receive surface acoustic wave (SAW) filter may be used as a hardware structure rather than IIP2 calibration.
A conventional method of calibrating IIP2 is possible for some TDD bands. A method of inserting a circuit for IIP2 measurement into a transceiver may be attempted for IIP2 calibration. However, there are problems such as integration and internal interference and it is difficult to be universally used.
It may be difficult to apply a conventional IIP2 calibration method to an FDD band. In implementing an FDD band, a duplexer may remove a leakage signal on a receive path (e.g., a leakage signal due to a transmit signal) due to the nature of its component. However, since an amount in which a signal is removed at intervals of a few Hz varies according to a frequency, it is difficult to perform IIP2 calibration.